| 1 | /* |
| 2 | * Elite - The New Kind. |
| 3 | * |
| 4 | * Reverse engineered from the BBC disk version of Elite. |
| 5 | * Additional material by C.J.Pinder. |
| 6 | * |
| 7 | * The original Elite code is (C) I.Bell & D.Braben 1984. |
| 8 | * This version re-engineered in C by C.J.Pinder 1999-2001. |
| 9 | * |
| 10 | * email: <christian@newkind.co.uk> |
| 11 | * |
| 12 | */ |
| 13 | |
| 14 | |
| 15 | /* |
| 16 | * The original Elite code did all the vector calculations using 8-bit integers. |
| 17 | * |
| 18 | * Writing all the routines in C to use 8 bit ints would have been fairly pointless. |
| 19 | * I have, therefore, written a new set of routines which use floating point math. |
| 20 | */ |
| 21 | |
| 22 | #include <stdlib.h> |
| 23 | #include <math.h> |
| 24 | |
| 25 | #include "config.h" |
| 26 | #include "vector.h" |
| 27 | |
| 28 | |
| 29 | |
| 30 | static Matrix start_matrix = |
| 31 | { |
| 32 | {1.0, 0.0, 0.0}, |
| 33 | {0.0, 1.0, 0.0}, |
| 34 | {0.0, 0.0,-1.0} |
| 35 | }; |
| 36 | |
| 37 | |
| 38 | |
| 39 | /* |
| 40 | * Multiply first matrix by second matrix. |
| 41 | * Put result into first matrix. |
| 42 | */ |
| 43 | |
| 44 | |
| 45 | void mult_matrix (struct vector *first, struct vector *second) |
| 46 | { |
| 47 | int i; |
| 48 | Matrix rv; |
| 49 | |
| 50 | for (i = 0; i < 3; i++) |
| 51 | { |
| 52 | |
| 53 | rv[i].x = (first[0].x * second[i].x) + |
| 54 | (first[1].x * second[i].y) + |
| 55 | (first[2].x * second[i].z); |
| 56 | |
| 57 | rv[i].y = (first[0].y * second[i].x) + |
| 58 | (first[1].y * second[i].y) + |
| 59 | (first[2].y * second[i].z); |
| 60 | |
| 61 | rv[i].z = (first[0].z * second[i].x) + |
| 62 | (first[1].z * second[i].y) + |
| 63 | (first[2].z * second[i].z); |
| 64 | } |
| 65 | |
| 66 | for (i = 0; i < 3; i++) |
| 67 | first[i] = rv[i]; |
| 68 | } |
| 69 | |
| 70 | |
| 71 | |
| 72 | |
| 73 | void mult_vector (struct vector *vec, struct vector *mat) |
| 74 | { |
| 75 | double x; |
| 76 | double y; |
| 77 | double z; |
| 78 | |
| 79 | x = (vec->x * mat[0].x) + |
| 80 | (vec->y * mat[0].y) + |
| 81 | (vec->z * mat[0].z); |
| 82 | |
| 83 | y = (vec->x * mat[1].x) + |
| 84 | (vec->y * mat[1].y) + |
| 85 | (vec->z * mat[1].z); |
| 86 | |
| 87 | z = (vec->x * mat[2].x) + |
| 88 | (vec->y * mat[2].y) + |
| 89 | (vec->z * mat[2].z); |
| 90 | |
| 91 | vec->x = x; |
| 92 | vec->y = y; |
| 93 | vec->z = z; |
| 94 | } |
| 95 | |
| 96 | |
| 97 | /* |
| 98 | * Calculate the dot product of two vectors sharing a common point. |
| 99 | * Returns the cosine of the angle between the two vectors. |
| 100 | */ |
| 101 | |
| 102 | |
| 103 | double vector_dot_product (struct vector *first, struct vector *second) |
| 104 | { |
| 105 | return (first->x * second->x) + (first->y * second->y) + (first->z * second->z); |
| 106 | } |
| 107 | |
| 108 | |
| 109 | |
| 110 | /* |
| 111 | * Convert a vector into a vector of unit (1) length. |
| 112 | */ |
| 113 | |
| 114 | struct vector unit_vector (struct vector *vec) |
| 115 | { |
| 116 | double lx,ly,lz; |
| 117 | double uni; |
| 118 | struct vector res; |
| 119 | |
| 120 | lx = vec->x; |
| 121 | ly = vec->y; |
| 122 | lz = vec->z; |
| 123 | |
| 124 | uni = sqrt (lx * lx + ly * ly + lz * lz); |
| 125 | |
| 126 | res.x = lx / uni; |
| 127 | res.y = ly / uni; |
| 128 | res.z = lz / uni; |
| 129 | |
| 130 | return res; |
| 131 | } |
| 132 | |
| 133 | |
| 134 | |
| 135 | |
| 136 | |
| 137 | void set_init_matrix (struct vector *mat) |
| 138 | { |
| 139 | int i; |
| 140 | |
| 141 | for (i = 0; i < 3; i++) |
| 142 | mat[i] = start_matrix[i]; |
| 143 | } |
| 144 | |
| 145 | |
| 146 | |
| 147 | void tidy_matrix (struct vector *mat) |
| 148 | { |
| 149 | mat[2] = unit_vector (&mat[2]); |
| 150 | |
| 151 | if ((mat[2].x > -1) && (mat[2].x < 1)) |
| 152 | { |
| 153 | if ((mat[2].y > -1) && (mat[2].y < 1)) |
| 154 | { |
| 155 | mat[1].z = -(mat[2].x * mat[1].x + mat[2].y * mat[1].y) / mat[2].z; |
| 156 | } |
| 157 | else |
| 158 | { |
| 159 | mat[1].y = -(mat[2].x * mat[1].x + mat[2].z * mat[1].z) / mat[2].y; |
| 160 | } |
| 161 | } |
| 162 | else |
| 163 | { |
| 164 | mat[1].x = -(mat[2].y * mat[1].y + mat[2].z * mat[1].z) / mat[2].x; |
| 165 | } |
| 166 | |
| 167 | mat[1] = unit_vector (&mat[1]); |
| 168 | |
| 169 | |
| 170 | /* xyzzy... nothing happens. :-)*/ |
| 171 | |
| 172 | mat[0].x = mat[1].y * mat[2].z - mat[1].z * mat[2].y; |
| 173 | mat[0].y = mat[1].z * mat[2].x - mat[1].x * mat[2].z; |
| 174 | mat[0].z = mat[1].x * mat[2].y - mat[1].y * mat[2].x; |
| 175 | } |
| 176 | |